Topic: Math between different records
Could you please recommend elegant way (read - best practices in "Rails way", less DB calls) to solve the following situation ?
I have 2 tables:
- has_many :meter_records
- belong_to :meter
I have to calculate difference between meter's current month record and same meter's previous month record.
I would like to avoid unnecessary selects from DB and also avoid dealing with SQL - I prefer functionality provided by ActiveRecord.
Can you please recommend the solution or at least point me to a good tutorial ?
Thank you in advance.
Last edited by artbar (2011-04-06 14:53:36)